With the development of the electronic information technology, the amount of data to be transmitted and processed is ever increasing. Especially in fields of video transmission, data storage and the like, the amount of data to be transmitted increases with the increasing image resolution and storage space. Currently, a commercial serial interface transmits data at about 10 Gbps. When a signal is transmitted at such a high speed, reflection, crosstalk, standing waves, and the like may occur in the transmitted signal due to impedance mismatch, which has a serious impact on the signal quality, damages signal integrity, and affects reception of a receiver. Therefore, for a high-speed signal transmission circuit, a calibration circuit module is generally provided to perform matching and calibration on an output impedance of a transmitter to improve the signal transmission quality.
The calibration circuit module mainly includes adjustable resistors and a constant current source. Resistors having resistances proportional to a resistance of a termination resistor may function as adjustable resistors of the calibration circuit module. There may be multiple such resistors, which occupy a large area. The constant current source is used in combination with the adjustable resistors. In order to achieve a high accuracy and reduce an error of the current source, the constant current source generally has a great size, i.e., occupies a large area. In addition, the adjustable resistors are obtained by duplicating the termination resistor. Since an error exists between the duplicated adjustable resistor and the real resistor (i.e., the termination resistor), the configuration obtained by calibration may not be optimal. Further, the calibration circuit module is idle when the calibration is not performed, thus the calibration circuit has low utilization.